The splicing of such fiber trunks requires alignment of their adjoining ends and with a minimum axial offset in order to avoid excessive losses of luminous energy at their junctions. When the fiber trunks are to be permanently interconnected, their ends may be bonded to each other with the aid of a transparent cement whose refractive index substantially matches that of the fibers. Thermal fusion may also be used for this purpose.
The alignment problem can be solved by the use of closely fitting sleeves or grooved guides in which the fiber extremities are permanently retained. The provision of such attachments, however, is cumbersome especially in the case of optical cables comprising a large number of fibers.